1. Field of the Invention
This invention relates to an improved device for trimming hedge, bushes and other ornamental plants and shrubs used in landscape gardening. Nearly everyone is familiar with and rejoices in the use and/or the results achieved with rotating monofilament lawn edgers and trimmers such as the WEEDEATER.RTM. for cutting grasses and small weed plants along or near curbs, driveways, walks, foundations, tree trunks, etc. Such devices are effective and safe for this purpose. They are not entirely satisfactory for cutting the tougher, thicker stems of the larger plants. Better means for accomplishing this purpose is the object of this invention.
2. The Prior Art
Other approaches have been used for this latter purpose. Thus, U.S. Pat. No. 3,050,854 issued Aug. 28, 1962 to J. Becker et al discloses a rotary hedge trimmer utilizing an electric motor to drive a relatively heavy cutting blade, which is wider at the outer ends than at the center and which has serrated edges sharpened to a knife edge to cut the hedge. While this device is effective for trimming hedge, the blade is relatively heavy and requires sharpening at frequent intervals. The motor required to drive such a heavy blade is apt to be heavy too, and relatively slow. Such a combination, while effective, could be tiring and dangerous if dropped or entangled in the limbs of a hedge or bush.
U.S. Pat. No. 3,417,420 issued Dec. 24, 1968 to L. B. Damon discloses a hedge trimmer involving a heavy blade, which operates similar to Becker in U.S. Pat. No. 3,050,854, except that Damon has two switches in series, both of which have to be held "on" with the operator's two hands in order to keep the motor running. Damon was quite concerned about the safety aspect of this and similar tools. His system of switches and a motor brake were designed to stop the motor immediately so the heavy blade would not injure the operator if the tool were dropped or were jerked out of his hand. Damon made no provision for an extension handle on his tool.
U.S. Pat. No. 3,693,255 issued Sept. 26, 1972 to J. Langenstein discloses a lawn edge trimmer utilizing a motor with a shaft and a hub or spool from which extends the end of a synthetic resin (plastic) wire, which is spun about the motor axis and acts as a cutting element. The handle on this device is detachable so the basic motor unit can be used for other purposes such as hedge trimming. Such a device would be relatively light and safe for such use, but the single synthetic resin wire envisioned has the disadvantages of cutting heavy hedge slowly and needing replacement at frequent intervals.
U.S. Pat. No. 4,062,115 issued Dec. 13, 1977 to W. R. Lee discloses a rotary garden cutter utilizing a multiplicity of flexible plastic lines attached to the periphery of a rapidly rotating hub. New lines can be installed quickly and easily as old lines become worn or break off. Lee points out that these flexible lines have a relatively short life and he discusses some of the approaches that have been tried to solve this problem. His preferred material for these lines is nylon monofilament of about 0.1 inches in diameter for rotation speeds of about 3600 revolutions per minute (RPM). The cutter can be used on the end of a long power wand or in a hand drill.
U.S. Pat. No. 4,202,094 issued May 13, 1980 to Kalmar discloses another single filament grass cutting attachment for mounting on a hand drill which includes a spool of plastic filament in the center of a hub to facilitate replacement of the filament as it wears. Kalmar recognizes flail-type mowers with which grass is cut by means of a flail or flexible length of material which may be a length of wire, cord, or even linked rigid members as in a chain. However, Kalmar concludes that this type of lawn mower is generally as expensive as a conventional lawn mower, because the difference between the cost of cutting blades and flails are negligible in comparison to the cost of the motors and chassis required for either of these options. Her objectives were similar to Langenstein's in that she wanted to (1) save money as compared to buying an expensive lawn mower, and (2) find another use for the familiar hand drill.
Thus, Applicant's device is an improvement over these methods in that a metal wire whip is rotated at a very high speed (i.e. .about.17,000 RPM) and used to cut hedge effectively, while a choice of handles provides convenience for use on low, high and intermediate-sized hedge and/or bushes. The wire whip does not flail; it cuts like plastic filament except that it is stronger and tougher than plastic, so it lasts much longer in use. It can cut the heavier stems of hedge and brush quicker and better than plastic filaments or strings.
The Applicant's wire cutter blade is also softer and more flexible than the heavy rigid blades of Becker and Damon. Therefore, it is intrinsically safer for the operator and, in addition, a system of parallel switches, an adjustable whip and chip guard, and two interchangeable handles provide additional safety and convenience.
The wire whip for cutting relatively coarse-stemmed foliage can be easily replaced when damaged or worn by simply sticking a new wire through a hole and tightening a set screw. Suitable wires can be made of various metals, alloys and/or space age composite materials to optimize performance. We have found that a small scrap of 12 to 14 gage copper bus wire, or some such material, will cut hedge about five times faster than a filament or blade cutter and the job is done safely, smoothly, quickly, quietly and easily. Obviously, any of these three devices is a great improvement over the old fashioned manual scissors-type cutters, and much quieter and safer than the reciprocating, saw-tooth type of power tools.